[Intel-gfx] [PATCH] drm/i915: Wait for the mutex whilst the reaper runs

[Chris Wilson]

On Wed, 10 Oct 2012 12:07:30 +0100, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> If the system is forced to start kswapd to recover pages, the system is
> very starved. Fortunately, kswapd is its own process context and can
> wait for the mutex.

Note this doesn't survive inspection with lockdep due to dependency upon
pfmemalloc_wait in the direct reclaim path - that is, it is possible for
__GFP_FS allocations to wait indefinitely upon kswapd (who in turn may
be waiting for the dev->struct_mutex held by the direct reclaimer). As
we don't have complete control over all allocations made whilst holding
the struct_mutex, we can't control the gfp_t to avoid the deadlock.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre